This invention relates to a process for the preparation of secondary alkanol alkoxylates. More particularly, the invention relates to the preparation of alkoxylates from C.sub.8 to C.sub.20 olefins, via a process that includes a sulfation step in which the olefins and sulfuric acid are introduced into a reaction zone for preparation of C.sub.8 to C.sub.20 monoalkyl sulfuric acids and an alkoxylation step in which the monoalkyl sulfuric acids and certain alkylene glycols and/or polyether glycols are reacted under specified conditions of temperature and residence time to yield the alkoxylates.
Secondary alkanol alkoxylates, as the terminology is used herein, are compounds of the general formula EQU R--O--Z--.sub.x H
wherein R is secondary alkyl, x is an integer, and Z represents an oxyalkylene group. The alkoxylates of particular interest to the invention include the ethoxylates for which each Z is an oxyethylene group, the propoxylates for which each Z is an oxypropylene or oxyisopropylene group, and mixed alkoxylates having both ethoxy and propoxy ether groups. Compounds of the above formula in which the secondary alkyl portion of the molecule has a carbon number in the detergent range (i.e., C.sub.8 to C.sub.20) and x is an integer greater than about 2, have recognized utility relating to their surfactant properties; the ethoxylate compounds are particularly common as components of industrial detergent formulations. Alkoxylates in which x is an integer greater than or equal to one serve as intermediates in the manufacture of alkoxylates having a longer polyether chain in the molecule, i.e, a higher value of x.
Detergent-range secondary alkanol alkoxylates have heretofore been commercially prepared by the reaction of alkylene oxides with secondary alkanols. Unlike the more common detergent-range primary alkanol alkoxylates, the detergent-range secondary alkanol alkoxylates cannot be readily produced by direct alkaline-catalyzed reaction with the alkylene oxide, but have instead required an initial acid-catalyzed reaction between the alkylene oxide and the secondary alkanol to produce a "seed" alkoxylate, of the above formula with x typically having an average value no greater than about three. Further addition of alkylene oxide to the seed alkoxylate, if desired, can then be accomplished by reaction under alkaline conditions. Conventional processing for the preparation of detergent-range secondary alkanol alkoxylates in this manner is described, for instance, by C. A. Carter in U.S. Pat. No. 2,870,220. The detergent-range secondary alcohols used in the synthesis of alkoxylates under conventional practice have generally been prepared from detergent-range paraffins by oxidation in the presence of a borate catalyst. Relevant to the description of the present invention as a process for the preparation of C.sub.8 to C.sub.20 secondary alkanol alkoxylates from C.sub.8 to C.sub.20 olefins, it is known in the art that detergent-range secondary alkanols can also be prepared from detergent-range olefins by sulfation with concentrated sulfuric acid followed by hydrolysis.